The Economist's billboard campaign, created by BBDO in 2005, is a minimalist yet interactive display featuring a giant lightbulb that illuminates when people pass by. The simplicity of the design, with just the lightbulb and The Economist logo, cleverly associates the publication with ideas and enlightenment. The interactive element engages pedestrians, making the ad memorable and reinforcing The Economist's reputation for thought-provoking content.